Vertical memory device with a double word line structure

ABSTRACT

A memory device includes: a substrate; a bit line which is vertically oriented from the substrate; a plate line which is vertically oriented from the substrate; and a memory cell provided with a transistor and a capacitor that are positioned in a lateral arrangement between the bit line and the plate line, wherein the transistor includes: an active layer which is laterally oriented to be parallel to the substrate between the bit line and the capacitor; and a line-shaped lower word line and a line-shaped upper word line vertically stacked with the active layer therebetween and oriented to intersect with the active layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/728,174 filed on Dec. 27, 2019, which claims priority ofKorean Patent Application No. 10-2019-0024083, filed on Feb. 28, 2019.The entire disclosure of each of the foregoing applications isincorporated herein by reference in its entirety.

BACKGROUND 1. Field

Various embodiments of the present invention relate generally to asemiconductor device and, more particularly, to a memory device.

2. Description of the Related Art

Recently, the size of memory cells continues to be decreased in order toincrease the net die of a memory device.

As the size of the memory cell is miniaturized, a parasitic capacitancehas to be decreased while capacitance is increased. However, it isdifficult to increase the net die due to structural limitations of thememory cells.

SUMMARY

Embodiments of the present invention are directed to highly integratedvertical memory cell arrays, and a memory device including the highlyintegrated vertical memory cell arrays.

The memory device may exhibit increased memory cell density. The memorydevice may exhibit reduced parasitic capacitance.

In accordance with an embodiment of the present invention, a memorydevice includes: a substrate; a bit line which is vertically orientedfrom the substrate; a plate line which is vertically oriented from thesubstrate; and a memory cell provided with a transistor and a capacitorthat are positioned in a lateral arrangement between the bit line andthe plate line, wherein the transistor includes: an active layer whichis laterally oriented to be parallel to the substrate between the bitline and the capacitor; and a line-shaped lower word line and aline-shaped upper word line vertically stacked with the active layertherebetween and oriented to intersect with the active layer.

In accordance with another embodiment of the present invention, a memorydevice includes: a substrate; a bit line which is vertically orientedfrom the substrate; a plate line which is vertically oriented from thesubstrate; and a plurality of memory cells that are stacked in adirection perpendicular to the substrate between the bit line and theplate line, wherein each of the memory cells includes: a transistorprovided with an active layer which is laterally oriented to be parallelto the substrate between the bit line and the plate line, and a pair ofline-shaped word lines which are vertically stacked with the activelayer therebetween and extending to intersect with the active layer; anda capacitor provided with a cylindrical first node which is laterallyoriented to be parallel to the substrate between the transistor and theplate line, a second node, and a dielectric material between thecylindrical first node and the second node.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an equivalent circuit diagram illustrating a memory deviceaccording to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a mirror-like structuresharing a plate line of FIG. 1 .

FIG. 3 is an equivalent circuit diagram illustrating the mirror-likestructure shown in FIG. 2 .

FIG. 4 is a perspective view illustrating a mirror-like structuresharing a bit line shown in FIG. 1 .

FIG. 5 is a cross-sectional view illustrating the memory device shown inFIG. 1 .

FIG. 6 is a plan view illustrating the memory device shown in FIG. 1 .

FIG. 7 is a perspective view showing details of a memory cell.

FIG. 8 is a cross-sectional view taken in a direction A1-A1′ of FIG. 7 .

FIG. 9 is a plan view taken in a direction A2-A2′ of FIG. 7 .

FIG. 10 is a detailed perspective view of a capacitor.

FIGS. 11A to 11C are views illustrating a first node of a capacitorhaving a three-dimensional structure in accordance with anotherembodiment of the present invention.

FIGS. 12A and 12B are views illustrating a memory device in accordancewith another embodiment of the present invention.

DETAILED DESCRIPTION

Various embodiments of the present invention will be described below inmore detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Throughout the disclosure, like referencenumerals refer to like parts throughout the various figures andembodiments of the present invention.

The drawings are not necessarily to scale and, in some instances,proportions may have been exaggerated in order to clearly illustratefeatures of the embodiments. When a first layer is referred to as being“on” a second layer or “on” a substrate, it not only refers to a casewhere the first layer is formed directly on the second layer or thesubstrate but also to a case where a third layer exists between thefirst layer and the second layer or the substrate.

According to the following embodiments of the present invention, memorycell density may be increased and parasitic capacitance may be reducedby vertically stacking memory cells.

FIG. 1 is an equivalent circuit diagram illustrating a memory deviceaccording to an embodiment of the present invention. FIG. 2 is aperspective view illustrating a mirror-like structure 100A sharing aplate line of FIG. 1 . FIG. 3 is an equivalent circuit diagramillustrating the mirror-like structure shown in FIG. 2 . FIG. 4 is aperspective view illustrating a mirror-like structure 100B sharing a bitline shown in FIG. 1 . FIG. 5 is a cross-sectional view illustrating thememory device shown in FIG. 1 . FIG. 6 is a plan view illustrating thememory device shown in FIG. 1 .

The memory device 100 may include a peripheral structure 110 and amemory cell array stack MCA. The memory cell array stack MCA may bepositioned over the peripheral structure 110. The memory cell arraystack MCA may include a plurality of memory cell arrays MCA_(L) andMCA_(U). The positioning of the memory cell array MCA relatively to theperipheral structure 110 may vary according to various implementationsof the present invention. For example, according to another embodimentof the present invention, the memory cell array stack MCA may bepositioned under the peripheral structure 110. The memory cell arraystack MCA may include DRAM memory cell array.

The memory cell array stack MCA may include at least two memory cellarrays MCA_(L) and MCA_(U) stacked over the peripheral structure 110.The at least two memory cell arrays MCA_(L) and MCA_(U) may bevertically stacked over the peripheral structure 110. Generally, an nnumber of memory cell arrays may be stacked in the memory cell array,where n is an integer equal to or greater than 2. According to anembodiment, the at least two memory cell arrays MCA_(L) and MCA_(U) mayform one pair of memory cell arrays and the memory cell array stack MCAmay include a plurality of pairs of memory cell arrays stacked over theperipheral structure 110. The plurality of pairs of memory cell arraysmay be stacked vertically over the peripheral structure 110. In anotherembodiment, a plurality of pairs of memory cell arrays may be laterallyarranged over the peripheral structure 110, each pair being identical tothe pair of the at least two memory cell arrays MCA_(L) and MCA_(U).

The peripheral structure 110 may include a material suitable forsemiconductor processing including, for example, a semiconductormaterial. For example, the peripheral structure 110 may include asubstrate made of a semiconductor material, such as a silicon substrate,a monocrystalline silicon substrate, a polysilicon substrate, anamorphous silicon substrate, a silicon germanium substrate, amonocrystalline silicon germanium substrate, a polycrystalline silicongermanium substrate, a carbon-doped silicon substrate, or a combinationthereof. The peripheral structure 110 may include a single-layersemiconductor substrate. The peripheral structure 110 may include amulti-layer semiconductor substrate. The peripheral structure 110 mayinclude other semiconductor materials such as germanium. The peripheralstructure 110 may include a III/V-group semiconductor substrate, forexample, a compound semiconductor substrate such as GaAs. The peripheralstructure 110 may include an SOI (Silicon-On-Insulator) substrate. Theperipheral structure 110 may have a stacked structure of a semiconductorsubstrate and a dielectric material.

The surface of the peripheral structure 110 may include a surface of thesubstrate. For example, the surface of the peripheral structure 110 mayinclude a plane CP. The memory cell array stack MCA may be positionedvertically over the plane CP of the peripheral structure 110. The memorycell array stack MCA may be formed in a first direction D1 perpendicularto the surface, i.e., the plane CP, of the peripheral structure 110. Thefirst direction D1 may be a direction perpendicular to the plane CP, andthe second direction D2 and the third direction D3 may be directionsparallel to the plane CP. The second direction D2 and the thirddirection D3 may intersect with each other, and the first direction D1may intersect with the second direction D2 and the third direction D3.The two memory cell arrays MCA_(L) and MCA_(U) may be grouped as onepair and a plurality of the pairs may be vertically stacked over theperipheral structure 110 in the first direction D1.

The plane CP of the peripheral structure 110 may include a first planeCP1 and a second plane CP2. The first plane CP1 and the second plane CP2may be spaced apart from each other in a second direction D2 which isperpendicular to the first direction D1. The first plane CP1 and thesecond plane CP2 may be surfaces of the same material. The first planeCP1 and the second plane CP2 may be surfaces of different materials. Thefirst plane CP1 and the second plane CP2 may be electrically insulated.The plane CP may be provided by a dielectric material. The top surfaceof the peripheral structure 110 may provide the plane CP. The topsurface of the peripheral structure 110 may be of a substrate. The topsurface of the peripheral structure 110 may be of a dielectric materialor a conductive material. The first plane CP1 and the second plane CP2may be of a dielectric material or a conductive material. The firstplane CP1 may be of a conductive material and the second plane CP2 maybe of a dielectric material.

The peripheral structure 110 may include at least one peripheral circuitportion for controlling the memory cell array stack MCA. The at leastone peripheral circuit portion is formed under the memory cell arraystack MCA. The at least one peripheral circuit portion may include atleast one circuit selected from sense amplifiers and sub-word linedrivers.

The two memory cell arrays MCA_(L) and MCA_(U) may be arranged over theplane CP of the peripheral structure 110. For the sake of convenience indescription, the two memory cell arrays MCA_(L) and MCA_(U) may berespectively called a lower memory cell array MCA_(L) and an uppermemory cell array MCA_(U). A plurality of pairs each of which includesthe two memory cell arrays MCA_(L) and MCA_(U) may be laterally arrangedin a third direction D3 over the peripheral structure 110. For example,referring to FIGS. 2 and 3 , the lower memory cell arrays MCA_(L1) andMCA_(L2) may be laterally arranged along the third direction D3, and theupper memory cell arrays MCA_(U1) and MCA_(U2) may be laterally arrangedalong the third direction D3.

The memory cell array stack MCA may include a plurality of word linesWL_(L1), WL_(L2), WL_(L3), WL_(U1), WL_(U2), and WL_(U3), a plurality ofbit lines BL₁, BL₂, BL₃ and BL₄, a plurality of memory cells MC_(L1),MC_(L2) and MC_(L3), MC_(L4), MC_(L5), MC_(L6), MC_(U1), MC_(U2),MC_(U3), MC_(U4), MC_(U5) and MC_(U6), and a plurality of plate linesPL₁ and PL₂. The number of word lines, the number of bit lines, thenumber of memory cells, and the number of plate lines are not limitedand may vary according to various implementations of the presentinvention.

The lower memory cell array MCA_(L) may include a plurality of wordlines WL_(L1), WL_(L2) and WL_(L3), a plurality of bit lines BL₁, BL₂,BL₃ and BL₄, a plurality of memory cells MC_(L1), MC_(L2), MC_(L3),MC_(L4), MC_(L5) and MC_(L6), and a plurality of plate lines PL₁ andPL₂. The upper memory cell array MCA_(U) may include a plurality of wordlines WL_(U1), WL_(U2) and WL_(U3), a plurality of bit lines BL₁, BL₂,BL₃ and BL₄, a plurality of memory cells MC_(U1), MC_(U2), MC_(U3),MC_(U4), MC_(L5) and MC_(L6), and a plurality of plate lines PL₁ andPL₂.

The bit lines BL₁, BL₂, BL₃ and BL₄ may extend along the first verticaldirection D1 from the plane CP of the peripheral structure 110. Forexample, the bit lines BL₁, BL₂, BL₃ and BL₄ may extend along the firstvertical direction D1 from the substrate. The bit lines BL₁, BL₂, BL₃and BL₄ may each be in direct contact with the plane CP of theperipheral structure 110. The bit lines BL₁, BL₂, BL₃ and BL₄ may bevertically oriented from a plane CP. The bit lines BL₁, BL₂, BL₃ and BL₄may be referred to as vertically oriented bit lines VBL. The bit linesBL₁, BL₂, BL₃ and BL₄ may be parallel to each other while spaced apartfrom each other. The bit lines BL₁, BL₂, BL₃ and BL₄ may beindependently arranged laterally while spaced apart from each other inthe second direction D2 and the third direction D3. The bit lines BL₁and BL₂ may be arranged independently along the second direction D2. Thebit lines BL₁ and BL₃ may be independently arranged along the thirddirection D3. The bit lines BL₂ and BL₄ may be independently arrangedalong the third direction D3.

Memory cell MC_(L1) may be coupled to bit line BL₁. Memory cell MC_(U1)may be coupled to bit line BL₁. Memory cells MC_(L1) and MC_(U1) may bearranged vertically along the first direction D1 and may be coupled tobit line BL₁. The lower memory cell array MCA_(L) and the upper memorycell array MCA_(U) may share bit line BL₁. Memory cells MC_(L1) andMC_(U1) may be stacked vertically from the plane CP between the bit lineBL₁ and the plate line PL₁. Bit line BL₃ may be positioned laterallyaway from the bit line BL₁ along the third direction D3. The bit lineBL₃ may be vertically oriented from the plane CP. Memory cells MC_(L3)and MC_(U3) may be stacked vertically from the plane CP between the bitline BL₃ and the plate line PL₁. The memory cells MC_(L1) and MC_(U1)may each be commonly coupled with the plate line PL₁ and the bit lineBL₁. The memory cells MC_(L3) and MC_(U3) may each be commonly coupledwith the plate line PL₁ and the bit line BL₃.

Referring now to the bit line BL₂, memory cell MC_(L2) may be coupled tothe bit line BL₂. Memory cell MC_(U2) may be coupled to the bit lineBL₂. Memory cells MC_(L2) and MC_(U2) may be arranged vertically in thefirst direction D1 and may be coupled to bit line BL₂. The lower memorycell array MCA_(L) and the upper memory cell array MCA_(U) may share bitline BL₂. Bit line BL₄ may be positioned laterally away from the bitline BL₂ along the third direction D3. The bit line BL₄ may bevertically oriented from the plane CP. Memory cells MC_(L4) and MC_(U4)may be stacked vertically from the plane CP between the bit line BL₄ andthe plate line PL₁. Memory cells MC_(L2) and MC_(U2) may be stackedvertically from the plane CP between the bit line BL₂ and the plate linePL₁. The memory cells MC_(L2) and MC_(U2) may each be commonly coupledwith plate line PL₁ and the bit line BL₂. The memory cells MC_(L4) andMC_(U4) may each be commonly coupled with plate line PL₁ and the bitline BL₄.

Memory cell MC_(L3) may be coupled to the bit line BL₃. Memory cellMC_(U3) may be coupled to the bit line BL₃. Memory cells MC_(L3) andMC_(U3) arranged vertically in the first direction D1 may be coupled tothe bit line BL₃. The lower memory cell array MCA_(L) and the uppermemory cell array MCA_(U) may share the bit line BL₃.

Memory cell MC_(L4) may be coupled to bit line BL₄. Memory cell MC_(U4)may be coupled to bit line BL₄. Memory cells MC_(L4) and MC_(U4)arranged vertically in the first direction D1 may be coupled to the bitline BL₄. The lower memory cell array MCA_(L) and the upper memory cellarray MCA_(U) may share the bit line BL₄.

As described above, the lower memory cell array MCA_(L) may include thebit lines BL₁, BL₂, BL₃ and BL₄. The upper memory cell array MCA_(U) mayinclude the bit lines BL₁, BL₂, BL₃ and BL₄. The lower memory cell arrayMCA_(L) and the upper memory cell array MCA_(U) may each be commonlycoupled with each of the bit lines BL₁, BL₂, BL₃ and BL₄.

The word lines WL_(L1), WL_(L2), WL_(U1), WL_(U2), WL_(L3) and WL_(U3)may be parallel to the surface of the peripheral structure 110 and mayeach extend in the third direction D3 which intersects with the firstdirection D1. The word lines WL_(L1), WL_(L2), WL_(U1), WL_(U2), WL_(L3)and WL_(U3) may be referred to as lateral word lines. The word linesWL_(L1), WL_(L2), WL_(U1), WL_(U2), WL_(L3) and WL_(U3) may be arrangedin a direction intersecting with the bit lines BL₁, BL₂, BL₃ and BL₄.The word lines WL_(L1), WL_(L2) and WL_(L3) may be positioned at a firstlevel in the first direction D1. The word lines WL_(L1), WL_(L2) andWL_(L3) may be positioned in the lower memory cell array MCA_(L). Theword lines WL_(L1), WL_(L2) and WL_(L3) may be arranged at a regularinterval along the second direction D2 and may each extend in the thirddirection D3. The word lines WL_(U1), WL_(U2) and WL_(U3) may bepositioned at a second level in the first direction D1. The word linesWL_(U1), WL_(U2) and WL_(U3) may be positioned in the upper memory cellarray MCA_(U). The word lines WL_(U1), WL_(U2) and WL_(U3) may bearranged at a regular interval along the second direction D2 and mayeach extend in the third direction D3. The second level may be furtheraway from the peripheral structure 110 than the first level.

Referring now to the word line WL_(L1), memory cell MC_(L1) may becoupled to the word line WL_(L1). Memory cell MC_(L3) may be coupled tothe word line WL_(L1). Memory cells MC_(L1) and MC_(L3) may be laterallyarranged while spaced apart from each other along the third direction D3may be coupled to the word line WL_(L1). It is noted that reference to aword line being connected with a memory cell means that the gate of theword line is coupled with the word line.

Memory cell MC_(L2) may be coupled to the word line WL_(L2). Memory cellMC_(L4) may be coupled to the word line WL_(L2). Memory cells MC_(L2)and MC_(L4) may be laterally arranged while spaced apart from each otheralong the third direction D3 and may be coupled to the word lineWL_(L2).

Memory cell MC_(L5) may be coupled to the word line WL_(L3). Memory cellMC_(L6) may be coupled to the word line WL_(L3). Memory cells MC_(L5)and MC_(L6) may be laterally arranged while spaced apart from each otheralong the third direction D3 and may be coupled to the word lineWL_(L3).

Memory cell MC_(U1) may be coupled to the word line WL_(U1). Memory cellMC_(U3) may be coupled to the word line WL_(U1). Memory cells MC_(U1)and MC_(U3) may be laterally arranged while spaced apart from each otheralong the third direction D3 and may be coupled to the word lineWL_(U1).

Memory cell MC_(U2) may be coupled to the word line WL_(U2). Memory cellMC_(U4) may be coupled to the word line WL_(U2). Memory cells MC_(U2)and MC_(U4) may be laterally arranged while spaced apart from each otheralong the third direction D3 and may be coupled to the word lineWL_(U2).

Memory cell MC_(U5) may be coupled to the word line WL_(U3). Memory cellMC_(U6) may be coupled to the word line WL_(U3). Memory cells MC_(U5)and MC_(U6) may be laterally arranged while spaced apart from each otheralong the third direction D3 and may be coupled to the word lineWL_(U3).

As described above, the lower memory cell array MCA_(L) may include theword lines WL_(L1), WL_(L2) and WL_(L3) that are parallel to each otherwhile spaced apart from each other in the second direction D2, and theupper memory cell array MCA_(U) may include the word lines WL_(U1),WL_(U2) and WL_(U3) that are parallel to each other while spaced apartfrom each other in the second direction D2.

Referring to FIG. 3 , in an embodiment second plane CP2 may be disposedbetween left and right first planes CP1. The word line WL_(L1) of thelower memory cell array MCA_(L) and the word line WL_(U1) of the uppermemory cell array MCA_(U) may be spaced apart from each other andarranged vertically from the left first plane CP1 in the first directionD1. The word line WL_(L2) of the lower memory cell array MCA_(L) and theword line WL_(U2) of the upper memory cell array MCA_(U) may be spacedapart from each other and arranged vertically from the second plane CP2in the first direction D1. The word line WL_(L3) of the lower memorycell array MCA_(L) and the word line WL_(U3) of the upper memory cellarray MCA_(U) may be spaced apart from each other and arrangedvertically from the right first plane CP1 in the first direction D1.

The lower memory cell array MCA_(L) and the upper memory cell arrayMCA_(U) may each share plate line PL₁ and PL₂. (See FIG. 1 ) The platelines PL₁ and PL₂ may each be oriented vertically from the plane CP ofthe peripheral structure 110 in the first direction D1. The plate linesPL₁ and PL₂ may be in direct contact with the plane CP of the peripheralstructure 110 as illustrated in FIG. 1 . However, according to avariation of the described embodiment, the plate lines PL₁ and PL₂ maynot contact the plane CP of the peripheral structure 110. The platelines PL₁ and PL₂ may intersect with the word lines WL_(L1), WL_(L2),WL_(L3), WL_(U1), WL_(U2) and WL_(U3) and may be parallel to the bitlines BL₁, BL₂, BL₃ and BL₄. The plate lines PL₁ and PL₂ may be set to afixed potential (for example, a ground potential). According to theembodiment of the present invention, the plate lines PL₁ and PL₂ may beoriented in the first direction D1 vertically from the plane CP of theperipheral structure 110, and may be elongated in the direction D3intersecting with the first direction D1. The plate lines PL₁ and PL₂may be vertically oriented from the plane CP. For example, the platelines PL₁ and PL₂ may extend along the first vertical direction D1 fromthe substrate. The plate lines PL₁ and PL₂ may be referred to asvertical plate lines VPL. The plate lines PL₁ and PL₂ may belinear-shaped pillars extending laterally along the third direction D3while vertically oriented in the first direction D1.

The bit lines BL₁, BL₂, BL₃ and BL₄ and the plate lines PL₁ and PL₂ maybe spaced apart from each other over the plane CP. More specifically,the plate line PL₁ may be positioned between the bit lines BL₁ and BL₂along the second direction D2. Referring to FIG. 3 , the bit lines BL₁,BL₂, BL₃ and BL₄ may be coupled to the first plane CP1, and the platelines PL₁ and PL₂ may be coupled to the second plane CP2. Morespecifically, bit lines BL₁, and BL₃ may be coupled to the left firstplane CP1, the bit lines BL₂, and BL₄ may be coupled to the right firstplane CP1, the plate line PL₁ may be coupled to the second plane CP2which is shown disposed between the left and right planes CP1 and CP2,and the plate line PL₂ may be coupled to another second plane CP2 notshown in FIG. 3 . The bit lines BL₁, BL₂, BL₃ and BL₄ and the platelines PL₁ and PL₂ may be electrically insulated.

Each of the memory cells MC_(L1), MC_(L3), MC_(U1), and MC_(U3) may bepositioned between a plane defined by the bit lines BL₁ and BL₃ and aplane defined by the plate line PL₁. Each of the memory cells MC_(L2),MC_(L4), MC_(U2), and MC_(U4) may be positioned between a plane definedby the bit lines BL₂ and BL₄ and a plane defined by the plate line PL₂.The memory cells MC_(L1), MC_(L2), and MC_(L5), may be positioned in alateral arrangement (LA) in the second direction D2. The memory cellsMC_(U1), MC_(U2), and MC_(U5) may be positioned in a lateral arrangement(LA) in the second direction D2. The memory cells MC_(L3), MC_(L4), andMC_(L6), may be positioned in a lateral arrangement (LA) in the seconddirection D2 and the memory cells MC_(U3), MC_(U4), and MC_(U6), may bepositioned in a lateral arrangement (LA) in the second direction D2. Thememory cells MC_(L1), MC_(L2), MC_(L3), MC_(L4), MC_(L5), MC_(L6),MC_(U1), MC_(U2), MC_(U3), MC_(U4), MC_(U5), and MC_(U6) may bepositioned above the peripheral structure 110 which is spaced apart fromthe plane CP in four levels along the first direction D1, with eachlevel having two rows spaced apart along the third direction D3, eachrow extending in the second direction D2.

Memory cell MC_(L1) may be coupled to the plate line PL₁. Memory cellsMC_(L)U and MC_(U1) that are arranged vertically in the first directionD1 may be coupled to the plate line PL₁. Memory cells MC_(L)U andMC_(L2) may be laterally arranged while spaced apart from each other inthe second direction D2 and may be coupled to the plate line PL₁. Memorycells MC_(L1) and MC_(L3) may be laterally arranged while spaced apartfrom each other along the third direction D3 and may be coupled to theplate line PL₁.

The memory cells MC_(L1), MC_(L2), MC_(L3), MC_(L4), MC_(U1), MC_(U2),MC_(U3) and MC_(U4) may include transistors T_(L1), T_(L2), T_(L3),T_(L4), T_(U1), T_(U2), T_(U3) and T_(U4) and capacitors C_(L1), C_(L2),C_(L3), C_(L4), C_(U1), C_(U2), C_(U3) and C_(U4), respectively. Thetransistors T_(L1), T_(L3), T_(U1), and T_(U3) and their respectivecapacitors C_(L1), C_(L3), C_(U1), and C_(U3) may be positioned betweenthe plane defined by the bit lines BL₁, and BL₃ and the plane of theplate line PL₁. The transistors T_(L2), T_(L4), T_(U2), and T_(U4) andtheir respective capacitors C_(L2), C_(L4), C_(U2), and C_(U4) may bepositioned between the plane defined by the bit lines BL₂, and BL₄ andthe plane of plate line PL₂ in the second direction D2. Each of thetransistors T_(L1), T_(L2), T_(L3), T_(L4), T_(U1), T_(U2), T_(U3) andT_(U4) may be positioned in a lateral arrangement (LA) extending in thesecond direction D2 with its respective capacitor among the capacitorsC_(L1), C_(L2), C_(L3), C_(L4), C_(U1), C_(U2), C_(U3) and C_(U4). Eachof the capacitors C_(L1), C_(L2), C_(L3), C_(L4), C_(U1), C_(U2), C_(U3)and C_(U4) may be positioned between its respective transistor among thetransistors T_(L1), T_(L2), T_(L3), T_(L4), T_(U1), T_(U2), T_(U3) andT_(U4) and the plate line PL₁.

Referring to FIGS. 1, 2 and 3 , a mirror-like structure 100A sharing aplate line is described.

The memory cell MC_(L1) may include the transistor T_(L1) and thecapacitor C_(L1). One end of the transistor T_(L1) may be coupled to thebit line BL₁ and the other end of the transistor T_(L1) may be coupledto one end of the capacitor C_(L1). The other end of the capacitorC_(L1) may be coupled to the plate line PL₁. The memory cell MC_(L2) mayinclude the transistor T_(L2) and the capacitor C_(L2). One end of thetransistor T_(L2) may be coupled to the bit line BL₂ and the other endof the transistor T_(L2) may be coupled to one end of the capacitorC_(L2). The other end of the capacitor C_(L2) may be coupled to theplate line PL₁. As described above, the memory cells MC_(L), and MC_(L2)may be symmetrically disposed with reference to the plate line PL₁.

That is, the memory cells MC_(L1) and MC_(L2) may be arranged in amirror-like structure sharing the plate line PL₁ while being coupled todifferent bit lines BL₁ and BL₂. The memory cells MC_(L1) and MC_(L2)may be laterally arranged in the second direction D2 which is parallelto the plane CP.

Likewise, the memory cells MC_(L3) and MC_(L4) may be arranged in amirror-like structure sharing the plate line PL₁ while being coupled todifferent bit lines BL₃ and BL₄. The memory cells MC_(L3) and MC_(L4)may be laterally arranged in the second direction D2 which is parallelto the plane CP.

The memory cells MC_(U1) and MC_(U2) may be arranged in a mirror-likestructure sharing the plate line PL₁ while being coupled to differentbit lines BL₁ and BL₂. The memory cells MC_(U1) and MC_(U2) may belaterally arranged in the second direction D2 which is parallel to theplane CP.

The memory cells MC_(U3) and MC_(U4) may be arranged in a mirror-likestructure sharing the plate line PL₁ while being coupled to differentbit lines BL₃ and BL₄. The memory cells MC_(U3) and MC_(U4) may belaterally arranged in the second direction D2 which is parallel to theplane CP.

Referring to FIGS. 1 and 4 , a mirror-like structure 100B sharing a bitline is described.

The memory cell MC_(L2) may include the transistor T_(L2) and thecapacitor C_(L2). One end of the transistor T_(L2) may be coupled to thebit line BL₂ and the other end of the transistor T_(L2) may be coupledto one end of the capacitor C_(L2). The other end of the capacitorC_(L2) may be coupled to the plate line PL₁. The memory cell MC_(L5) mayinclude the transistor T_(L5) and the capacitor C_(L5). One end of thetransistor T_(L5) may be coupled to the bit line BL₂ and the other endof the transistor T_(L5) may be coupled to one end of the capacitorC_(L5). The other end of the capacitor C_(L5) may be coupled to theplate line PL₂. As described above, the memory cells MC_(L2) and MC_(L5)are symmetrically disposed with reference to the bit line BL₂.

That is, the memory cells MC_(L2) and MC_(L5) may be arranged in amirror-like structure sharing the bit line BL₂ while being coupled todifferent plate lines PL₁ and PL₂. The memory cells MC_(L2) and MC_(L5)may be laterally arranged in the second direction D2 which is parallelto the plane CP.

The memory cells MC_(L4) and MC_(L6) may be arranged in a mirror-likestructure sharing the bit line BL₄ while being coupled to differentplate lines PL₁ and PL₂. The memory cells MC_(L4) and MC_(L6) may belaterally arranged in the second direction D2 which is parallel to theplane CP.

The memory cells MC_(U2) and MC_(U5) may be arranged in a mirror-likestructure sharing the bit line BL₂ while being coupled to differentplate lines PL₁ and PL₂. The memory cells MC_(U2) and MC_(U5) may belaterally arranged in the second direction D2 which is parallel to theplane CP.

The memory cells MC_(U4) and MC_(U6) may be arranged in a mirror-likestructure sharing the bit line BL₄ while being coupled to differentplate lines PL₁ and PL₂. The memory cells MC_(U4) and MC_(U6) may belaterally arranged in the second direction D2 which is parallel to theplane CP.

The memory device 100 shown in FIG. 1 may include both of themirror-like structure 100A sharing a plate line and the mirror-likestructure 100B sharing a bit line.

FIG. 5 is a cross-sectional view illustrating a portion of the memorydevice 100 of FIG. 1 , illustrating memory cells coupled to the bitlines BL₁ and BL₂ and the plate lines PL₁ and PL₂.

Referring to FIGS. 1 to 5 , the memory device 100 may include a memorycell array stack MCA which is positioned above the peripheral structure110, and the memory cell array stack MCA may include a lower memory cellarray MCA_(L) and an upper memory cell array MCA_(U) that are verticallystacked. The memory device 100 may include bit lines BL₁ and BL₂ andplate lines PL₁ and PL₂ that are spaced apart from each other andvertically oriented relatively to the peripheral structure 110.

The memory cells MC_(L1) and MC_(U1) including transistors T_(L1) andT_(U1) and capacitors C_(L1) and C_(U1), respectively, may be formedbetween the bit line BL₁ and the plate line PL₁. Also, the memory cellsMC_(L2) and MC_(U2) including transistors T_(L2) and T_(U2) andcapacitors C_(L2) and C_(U2) respectively. The memory cells MC_(L5) andMC_(U5) including transistors T_(L5) and T_(U5) and capacitors C_(L5)and C_(U5) respectively, may be formed between the bit line BL₂ and theplate line PL₂. The memory cells MC_(L1), MC_(L2), and MC_(L5) may bepositioned at the same level in relation to the first direction D1 andin a lateral arrangement spaced apart from each other along the seconddirection D2. The memory cells MC_(U1), MC_(U2), and MC_(U5) may bepositioned at the same level in relation to the first direction D1 andin a lateral arrangement spaced apart from each other along the seconddirection D2. The transistor and capacitor forming each memory cell maybe arranged laterally to each other along the second direction D2.

Each of the transistors T_(L1), T_(L2), T_(L5), T_(U1), T_(U2) andT_(U5) may include an active layer ACT which is laterally oriented withrespect to the peripheral structure 110, and the active layer ACT mayinclude a first source/drain region T1, a channel CH, and a secondsource/drain region T2. The first source/drain region T1, the channelCH, and the second source/drain region T2 may be positioned in a lateralarrangement along the second direction D2 which is parallel to theperipheral structure 110. The transistors T_(L1), T_(L2), T_(L5),T_(U1), T_(U2) and T_(U5) may include word lines WL_(L1), WL_(L2),WL_(L5), WL_(U1), WL_(U2) and WL_(U5), respectively, and the word linesWL_(L1), WL_(L2), WL_(L5), WL_(U1), WL_(U2) and WL_(U5) may be in a lineshape extending so as to intersect with the active layer ACT. Asillustrated in FIG. 5 , the word lines WL_(L1), WL_(L2), WL_(L5),WL_(U1), WL_(U2) and WL_(U5) may be of a double word line structure inwhich the word lines are vertically stacked with the active layer ACTbetween them. Each of the word lines WL_(L1), WL_(L2), WL_(L5), WL_(U1),WL_(U2) and WL_(U5) may be composed of two conductive layers with theactive layer ACT therebetween. A gate dielectric layer GD may be formedbetween each of the word lines WL_(L1), WL_(L2), WL_(L5), WL_(U1),WL_(U2) and WL_(U5) and the corresponding active layer ACT.

The capacitors C_(L1), C_(L2), C_(L5), C_(U1), C_(U2) and C_(U5) mayeach include a first node N1, a second node N2, and a dielectricmaterial N3 between the first node N1 and the second node N2. The firstnode N1, the dielectric material N3, and the second node N2 may bepositioned in a lateral arrangement which is parallel to the peripheralstructure 110. According to the cross-sectional view of FIG. 5 , eachfirst node N1 may have a square bracket shape facing towards arespective plate line. Specifically, each first node N1 of thecapacitors C_(L1), C_(L2), C_(U1), and C_(U2) may have a square bracketshape (“[” or “]” facing towards the plate line PL₁ and each first nodeN1 of the capacitors C_(L5) and C_(U5) may have a square bracket shapefacing towards the plate line PL₂. Stated otherwise the first node N1may have a cylinder shape with on end of the cylinder being open. Thehorizontal parts of the bracket shape extending in the second directionD2 of each of the first nodes N1 may be longer than the part extendingin the first direction D1 as illustrated in FIG. 5 . The dielectricmaterial N3 may be formed conformally within the interior surface ofeach first node N1 to leave a central region within each first node N1to be filled with the second node N2. The second node N2 may extend fromthe respective plate line PL₁ or PL₂ to fill the inside of the centralregion of the first node N1. The dielectric material N3 may be disposedbetween each pair of first and second nodes N1 and N2.

Dielectric materials ILD may be formed between the lower memory cellsMC_(L1), MC_(L2) and MC_(L5) and the upper memory cells MC_(U1), MC_(U2)and MC_(U5) that are vertically stacked. Thus, in the memory cell arraystack MCA, the dielectric materials ILD may be positioned between thelower memory cell array MCA_(L) and the upper memory cell array MCA_(U).When a plurality of memory cell arrays are stacked, the lower memorycell arrays MCA_(L), the dielectric materials ILD, and the upper memorycell arrays MCA_(U) may be alternately stacked vertically.

FIG. 6 is a plan view illustrating the lower memory cell array MCA_(L)of the memory cell array stack MCA.

Referring to FIGS. 1 to 6 , the lower memory cell array MCA_(L) mayinclude bit lines BL₁, BL₂, BL₃ and BL₄ and plate lines PL₁ and PL₂. Thebit lines BL₁, BL₂, BL₃ and BL₄ and the plate lines PL₁ and PL₂ may bevertically oriented from the peripheral structure 110, individually. Thebit lines BL₁, BL₂, BL₃ and BL₄ and the plate lines PL₁ and PL₂ may bespaced apart from each other.

A memory cell MC_(L1) including a transistor T_(L1) and a capacitorC_(L1) that are positioned in a lateral arrangement (LA) between the bitline BL₁ and the plate line PL₁ may be formed. A memory cell MC_(L3)including a transistor T_(L3) and a capacitor C_(L3) that are positionedin a lateral arrangement (LA) between the bit line BL₃ and the plateline PL₁ may be formed. A memory cell MC_(L2) including a transistorT_(L2) and a capacitor C_(L2) that are positioned in a lateralarrangement (LA) between the bit line BL₂ and the plate line PL₁ may beformed. A memory cell MC_(L4) including a transistor T_(L4) and acapacitor C_(L4) that are positioned in a lateral arrangement (LA)between the bit line BL₄ and the plate line PL₁ may be formed.

A memory cell MC_(L5) including a transistor T_(L5) and a capacitorC_(L5) that are positioned in a lateral arrangement (LA) between the bitline BL₂ and the plate line PL₂ may be formed. A memory cell MC_(L6)including a transistor T_(L6) and a capacitor C_(L6) that are positionedin a lateral arrangement (LA) between the bit line BL₄ and the plateline PL₂ may be formed.

Each of the transistors T_(L1), T_(L2), T_(L3), T_(L4), T_(L5) andT_(L6) may include an active layer ACT which is laterally oriented withrespect to the peripheral structure 110, and the active layer ACT mayinclude a first source/drain region T1, a channel CH, and a secondsource/drain region T2. The first source/drain region T1, the channelCH, and the second source/drain region T2 may be positioned in a lateralarrangement LA which is parallel to the peripheral structure 110. Thetransistors T_(L1), T_(L2), may include the word line WL_(L1), thetransistors T_(L3), T_(L4), may include the word line WL_(L2) and thetransistors T_(L5) and T_(L6) may include the word line WL_(L3). Theword lines WL_(L1), WL_(L2) and WL_(L3) may each have a shape of a linethat extends in the third direction D3. The word lines WL_(L1), WL_(L2)and WL_(L3) may each have a shape of a line that extends in the thirddirection D3 to overlap with the active region ACT of the channel CH ofrespective transistors. Specifically, the word line WL_(L1), may overlapwith the active region ACT of the channel CH of transistors T_(L1) andT_(L3) the word lines WL_(L2), may overlap with the active region ACT ofthe channel CH of transistors T_(L2) and T_(L4), and the word lineWL_(L3), may overlap with the active region ACT of the channel CH oftransistors T_(L5) and T_(L6). The word lines WL_(L1), WL_(L2) andWL_(L3) may have a double word line structure in which the word linesWL_(L1), WL_(L2) and WL_(L3) are vertically stacked with the respectiveactive layers ACT between them. The transistors T_(L1) and T_(L3) mayeach be commonly coupled with word line WL_(L1), the transistors T_(L2)and T_(L4) may each be commonly coupled with word line WL_(L2), and thetransistors T_(L5) and T_(L6) may each be commonly coupled with wordline WL_(L3).

The capacitors C_(L1), C_(L2), C_(L3), C_(L4), C_(L5) and C_(L6) mayeach include the first node N1, the second node N2, and the dielectricmaterial N3 between the first node N1 and the second node N2. Accordingto the view of FIG. 6 , each first node N1 may have a square bracketshape facing towards a respective plate line. Specifically, each firstnode N1 of the capacitors C_(L1), C_(L2), C_(L3), and C_(L4) may have asquare bracket shape (“[” or “]” facing towards the plate line PL₁ andeach first node N1 of the capacitors C_(L5) and C_(L6) may have a squarebracket shape facing towards the plate line PL₂. The horizontal parts ofthe bracket shape extending in the second direction D2 of each of thefirst nodes N1 may be longer than the part extending in the thirddirection D3 as illustrated in FIG. 6 . The dielectric material N3 maybe formed conformally within the interior surface of each first node N1to leave a central region within each first node N1 to be filled withthe second node N2. The second node N2 may extend from the respectiveplate line PL₁ or PL₂ to fill the inside of the central region of thefirst node N1. The dielectric material N3 may be disposed between eachpair of first and second nodes N1 and N2.

FIG. 7 is a perspective view showing details of a memory cell. FIG. 8 isa cross-sectional view taken in a direction A1-A1′ of FIG. 7 . FIG. 9 isa plan view taken in a direction A2-A2′ of FIG. 7 . FIG. 10 is adetailed perspective view of a capacitor. FIGS. 7 to 10 illustrate thememory cell MC_(L1).

Referring to FIGS. 7 to 10 , the memory cell MCU may be positioned in alateral arrangement (LA) in the second direction D2 which is parallel tothe plane CP of the peripheral structure 110 between the bit line BL₁and the plate line PL₁.

The memory cell MC_(L1) may include a transistor T_(L1) and a capacitorC_(L1). The transistor T_(L1) and the capacitor Cu may be positioned ina lateral arrangement (LA) extending in the second direction D2 which isparallel to the plane CP of the peripheral structure 110.

The transistor T_(L1) may include an active layer ACT, a gate dielectriclayer GD, and a word line WL_(L1). The word line WL_(L1) may include anupper word line G1 and a lower word line G2. That is, the word lineWL_(L1) may have the double word line structure in which the upper andlower word lines G1 and G2 are stacked with the active layer ACTtherebetween.

The active layer ACT may include a first source/drain region T1 coupledto the bit line BL₁, a second source/drain region T2 coupled to thecapacitor C_(L1), and a channel CH positioned between the firstsource/drain region T1 and the second source/drain region T2. The activelayer ACT may be laterally oriented in the second direction D2 betweenthe bit line BL₁ and the capacitor CL₁. The active layer ACT may havethe shape of an elongated flat plate. The first source/drain region T1,the channel CH, and the second source/drain region T2 may be positionedin a lateral arrangement LA which is oriented in the second direction D2which is parallel to the plane CP. The first source/drain region T1, thesecond source/drain region T2, and the channel CH may be formed in theactive layer ACT. The active layer ACT may be formed to include anysuitable semiconductor material. For example, the active layer ACT mayinclude doped polysilicon, undoped polysilicon, or amorphous silicon.The first source/drain region T1 and the second source/drain region T2may be doped with an N-type impurity or a P-type impurity. The firstsource/drain region T1 and the second source/drain region T2 may bedoped with an impurity of the same conductivity type. The firstsource/drain region T1 and the second source/drain region T2 may includeat least one impurity selected from a group including arsenic (As),phosphorus (P), boron (B), indium (In), and combinations thereof. Insome embodiments of the present invention, the channel CH may be dopedwith a conductive impurity. Referring to FIG. 9 , the width of thechannel CH along the third direction D3 may be greater than the width ofthe first and second source/drain regions T1 and T2.

The upper word line G1 and the lower word line G2 may form a singlepair. The upper word line G1 and the lower word line G2 may bevertically stacked while spaced apart from each other in the firstdirection D1 with the channel CH interposed therebetween, and may beoriented along the third direction D3. The upper word line G1 and thelower word line G2 may be parallel to the plane CP, and extend along thethird direction D3 which is parallel to the second direction D2. Theupper word line G1 and the lower word line G2 may have a shape of linesextending along the third direction D3. The pair of the upper word lineG1 and the lower word line G2 may form a vertically stacked double gate.The upper word line G1 and the lower word line G2 may include asilicon-based material, a metal-based material, or a combinationthereof. The upper word line G1 and the lower word line G2 may includepolysilicon, titanium nitride, tungsten, aluminum, copper, tungstensilicide, titanium silicide, nickel silicide, cobalt silicide or acombination thereof.

The upper word line G1 and the lower word line G2 may be set to the samepotential, and one end of the upper word line G1 and one end of thelower word line G2 may be electrically connected to each other at an endof an array of units of mats or blocks of a plurality of memory cells.In an embodiment, the upper word line G1 and the lower word line G2 ofthe memory cells MCU may be connected to different nodes. The upper wordline G1 may be connected to a node for applying a first voltage, and thelower word line G2 may be connected to another node applied with asecond voltage. The first voltage and the second voltage are differentfrom each other. For example, the upper word line G1 may be applied witha word line driving voltage, the lower word line G2 may be applied witha ground voltage. The upper word line G1 and the lower word line G2 mayhave the same width in the second direction D2 and the same length alongthe third direction D3. The upper word line G1 and the lower word lineG2 may have the same thickness (dimension in the first direction D1).The upper word line G1, the lower word line G2, and the active layer ACTmay have the same thickness or different thicknesses. Both side edges ofthe upper word line G1 and both side edges of the lower word line G2 maybe aligned with each other. According to another embodiment of thepresent invention, both side edges of the upper word line G1 and bothside edges of the lower word line G2 may not be aligned with each other.The upper word line G1 and the lower word line G2 may overlap with thechannel CH of the active layer ACT in the first direction D1. The upperword line G1 and the lower word line G2 may partially cover the upperand lower portions of the active layer ACT. The upper word line G1 andthe lower word line G2 may be formed of a material which is differentfrom that of the active layer ACT. The upper word line G1 and the lowerword line G2 may be paired. The word line resistance may be loweredbecause a pair of word lines including the upper word line G1 and thelower word line G2 is formed. In addition, since a pair of the upperword line G1 and the lower word line G2 are formed, interference betweenthe memory cells that are vertically adjacent to each other may beprevented. For example, the lower word line G2 of the memory cellMC_(U1) may be provided between the upper word line G1 of the memorycell MC_(L1) and the upper word line G1 of the memory cell MC_(U1). Thelower word line G2 may be used to inhibit/prevent adjacent ones of theupper word lines G1 from being electrically coupled to each other.

The gate dielectric layer GD may be formed on the upper surface and thelower surface of the active layer ACT, individually. The gate dielectriclayer GD may include a first dielectric portion GD1 and a seconddielectric portion GD2. The first dielectric portion GD1 may be formedbetween the upper word line G1 and the channel CH, and the seconddielectric portion GD2 may be formed between the lower word line G2 andthe channel CH. The first dielectric portion GD1 may be discontinuousfrom the second dielectric portion GD2. The first dielectric portion GD1and the second dielectric portion GD2 may have the same thickness andmay be formed of the same material. The gate dielectric layer GD mayinclude silicon oxide, silicon nitride, or a combination thereof. Thegate dielectric layer GD may be formed by thermal oxidation of theactive layer ACT. According to another embodiment of the presentinvention, the gate dielectric GD may include a high dielectricmaterial, and the high dielectric material may include hafnium oxide(HfO₂), zirconium oxide (ZrO₂), aluminum oxide (Al₂O₃), lanthanum oxide(La₂O₃), titanium oxide (TiO₂), tantalum oxide (Ta₂O₅), niobium oxide(Nb₂O₅), or strontium titanium oxide (SrTiO₃). According to anotherembodiment of the present invention, the gate dielectric layer GD mayinclude a stack of silicon oxide and a high dielectric material, thesilicon oxide may be in direct contact with the channel CH, and the highdielectric material may be in direct contact with the upper word line G1and the lower word line G2.

The capacitor C_(L1) may include a first node N1 coupled to thetransistor T_(L1), a second node N2 coupled to the plate line PL₁, and adielectric material N3 disposed between the first node N1 and the secondnode N2. The dielectric material N3 may form a continuous layer betweenthe first node N1 and the second node N2. The first node N1, thedielectric material N3, and the second node N2 may be positioned in alateral arrangement which is parallel to the plane CP.

The first node N1 of the capacitor C_(L1) may have a three-dimensionalstructure. The first node N1 of the three-dimensional structure may be alateral three-dimensional structure which is parallel to the plane CP.As an example of the three-dimensional structure, the first node N1 ofthe capacitor C_(L1) may have a cylindrical shape, a pillar shape, or apylinder shape (i.e., a merged form of a pillar shape and a cylindricalshape). The first node N1 may include polysilicon, metal, noble metal, ametal nitride, a conductive metal oxide, a conductive noble metal oxide,a metal carbide, a metal silicide, or a combination thereof. Forexample, the first node N1 may include titanium (Ti), titanium nitride(TiN), tantalum (Ta), tantalum nitride (TaN), tungsten (W), tungstennitride (WN), ruthenium (Ru), ruthenium oxide (RuO₂), iridium (Ir),iridium oxide (IrO₂), platinum (Pt), molybdenum (Mo), molybdenum oxide(MoO), a stack of titanium nitride and tungsten (TiN/W), or a stack oftungsten nitride and tungsten (WN/W).

The second node N2 of the capacitor C_(L1) may have a branch shapeextending in the second direction D2 which is parallel to the plane CPfrom the plate line PL₁. The dielectric material N3 may have a shapesurrounding the second node N2 having a form of branch, and the firstnode N1 may have a shape surrounding the second node N2 with thedielectric material N3 interposed therebetween. For example, the firstnode N1 having a cylindrical shape may be electrically connected to thesecond source/drain region T2 of the transistor T_(L1), and the secondnode N2 may be positioned in the inside of the cylindrical shape of thefirst node N1, and the second node N2 may be electrically connected tothe plate line PL₁.

Referring to FIG. 10 , the second node N2 of the capacitor C_(L1) mayfurther include outer second nodes N21, N22, N23 and N24 coupled to theplate line PL₁. The outer second nodes N21, N22, N23 and N24 may bepositioned outside the first node N1 with the dielectric material N3interposed therebetween. The second node N2 may be abbreviated as an‘inner second node’, and the inner second node N2 may be positionedinside the cylindrical shape of the first node N1.

The outer second nodes N21, N22, N23 and N24 may be positioned tosurround the outer wall of the cylindrical shape of the first node N1.The outer second nodes N21, N22, N23 and N24 may be in continuum witheach other.

The capacitor C_(L1) may include a metal-insulator-metal (MIM)capacitor. The first node N1 and the second nodes N2, N21, N22, N23 andN24 may include a metal-based material, and the dielectric material N3may include silicon oxide, silicon nitride, or a combination thereof.The dielectric material N3 may include a high dielectric (high-k)material having a higher dielectric constant than that of silicon oxide(SiO₂) which has a dielectric constant of approximately 3.9. Thedielectric material N3 may include a high dielectric material having adielectric constant of approximately 4 or higher. The high dielectricmaterial may have a dielectric constant of approximately 20 or more. Thehigh dielectric material may include hafnium oxide (HfO₂), zirconiumoxide (ZrO₂), aluminum oxide (Al₂O₃), lanthanum oxide (La₂O₃), titaniumoxide (TiO₂), tantalum oxide (Ta₂O₅), niobium oxide (Nb₂O₅), orstrontium titanium oxide (SrTiO₃). According to another embodiment ofthe present invention, the dielectric material N3 may be a compositelayer including two or more layers of the aforementioned high-dielectricmaterials.

The first node N1 and the second nodes N2, N21, N22, N23 and N24 mayinclude a metal, a noble metal, a metal nitride, a conductive metaloxide, a conductive noble metal oxide, a metal carbide, a metalsilicide, or a combination thereof. For example, the first node N1 andthe second nodes N2, N21, N22, N23 and N24 may include titanium (Ti),titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), tungsten(W), tungsten nitride (WN), ruthenium (Ru), ruthenium oxide (RuO₂),iridium (Ir), iridium oxide (IrO₂), platinum (Pt), molybdenum (Mo),molybdenum oxide (MoO), a stack of titanium nitride/tungsten (TiN/W), astack of tungsten nitride/tungsten (WN/W). The first node N1 and thesecond nodes N2, N21 and N22 may include a combination of a metal-basedmaterial and a silicon-based material. For example, the second nodes N2,N21, N22, N23 and N24 may be a stack of titanium nitride/silicongermanium/tungsten nitride (TiN/SiGe/WN).

The dielectric material N3 may be formed of a zirconium-based oxide. Thedielectric material N3 may have a stack structure including zirconiumoxide (ZrO₂). The stack structure including zirconium oxide (ZrO₂) mayinclude a ZA (ZrO₂/Al₂O₃) stack or a ZAZ (ZrO₂/Al₂O₃/ZrO₂) stack. The ZAstack may be a structure in which aluminum oxide (Al₂O₃) stacked overzirconium oxide (ZrO₂), and zirconium oxide (ZrO₂) may contact the firstnode N1, while aluminum oxide (Al₂O₃) may contact the second node N2.The ZAZ stack may be a structure in which zirconium oxide (ZrO₂),aluminum oxide (Al₂O₃), and zirconium oxide (ZrO₂) are sequentiallystacked. The ZA stack and the ZAZ stack may be referred to as azirconium oxide-based layer. According to another embodiment of thepresent invention, the dielectric material N3 may be formed of ahafnium-based oxide. The dielectric material N3 may have a stackstructure including hafnium oxide (HfO₂). The stack structure includinghafnium oxide (HfO₂) may include an HA (HfO₂/Al₂O₃) stack or an HAH(HfO₂/Al₂O₃/HfO₂) stack. The HA stack may be a structure in whichaluminum oxide (Al₂O₃) is stacked over hafnium oxide (HfO₂), and hafniumoxide (HfO₂) may contact the first node N1, and aluminum oxide (Al₂O₃)may contact the second node N2. The HAH stack may be a structure inwhich hafnium oxide (HfO₂), aluminum oxide (Al₂O₃), and hafnium oxide(HfO₂) are sequentially stacked. The HA stack and the HAH stack may bereferred to as a hafnium oxide-based layer (HfO₂-based layer). In the ZAstack, the ZAZ stack, the HA stack, and the HAH stack, the aluminumoxide (Al₂O₃) may have a band gap energy which is larger than those ofzirconium oxide (ZrO₂) and hafnium oxide (HfO₂). Aluminum oxide (Al₂O₃)may have a lower dielectric constant than zirconium oxide (ZrO₂) andhafnium oxide (HfO₂). Thus, the dielectric material N3 may include astack of a high dielectric material and a high-band gap energy materialwhose band gap energy is greater than the high dielectric material. Thedielectric material N3 may include silicon oxide (SiO₂) as anotherhigh-band gap energy material other than aluminum oxide (Al₂O₃). Thedielectric material N3 may include a high-band gap energy material sothat the leakage current may be suppressed. The high-band gap energymaterial may be extremely thin. The high-band gap energy material may bethinner than the high dielectric material.

According to another embodiment of the present invention, the dielectricmaterial N3 may have a laminated structure in which a high dielectricmaterial and a high-band gap material are alternately stacked. Forexample, the dielectric material N3 may have ZAZA(ZrO₂/Al₂O₃/ZrO₂/Al₂O₃), ZAZAZ (ZrO₂/Al₂O₃/ZrO₂/Al₂O₃/ZrO₂), HAHA(HfO₂/Al₂O₃/HfO₂/Al₂O₃) or HAHAH (HfO₂/Al₂O₃/HfO₂/Al₂O₃/HfO₂). In thelaminated structure, the aluminum oxide (Al₂O₃) may be extremely thin.

According to another embodiment of the present invention, the dielectricmaterial N3 may include a stack structure, a laminated structure or aninter-mixing structure including zirconium oxide, hafnium oxide, andaluminum oxide.

According to another embodiment of the present invention, an interfacecontrolling layer may be further formed to improve the leakage currentbetween the first node N1 and the dielectric material N3. The interfacecontrolling layer may include titanium oxide (TiO₂).

The interface controlling layer may be formed between the second node N2and the dielectric material N3.

The bit line BL₁ and the plate line PL₁ may include a silicon-basedmaterial, a metal-base material or a combination thereof. The bit lineBL₁ may include polysilicon, titanium nitride, tungsten, or acombination thereof. For example, the bit line BL₁ may includepolysilicon doped with an N-type impurity or titanium nitride (TiN). Thebit line BL₁ may include a stack of titanium nitride and tungsten(TiN/W).

An ohmic contact such as a metal silicide may be further formed betweenthe bit line BL₁ and the first source/drain region T1 of the transistorT_(L1). The plate line PL₁ may be formed of the same material as that ofthe second nodes N2, N21, N22, N23 and N24. The plate line PL₁ and thesecond nodes N2, N21, N22, N23 and N24 may be formed simultaneously.

The bit line BL₁ may have a form of a pillar vertically extending fromthe plane CP in the first direction D1. A cross-section of the bit lineBL₁ taken in the second direction D2 may be circle-shaped oroval-shaped. The pillar-shaped bit line BL₁ may have a low resistance.

The plate line PL₁ may be a linear shape vertically extending from theplane CP in the first direction D1. The cross-sections of the plate linePL₁ in the first, second direction, and third directions D1, D2, and D3may be rectangles of different areas. The plate line PL₁ may have awidth (dimension in the second direction D2) that is smaller than itslength (dimension in the third direction D3) and also smaller than itsheight (dimension in the first direction D1). More specifically, thewidth (dimension in the second direction D2) of the plate line PL₁ maybe the same as the width (dimension in the second direction D2) of theword line W_(L1) as shown in FIG. 7 . The height (dimension in the firstdirection D1) of the plate line PL₁ may be such that the top surface ofthe plate line PL₁ is positioned higher than a top surface of a node N1of a capacitor (e.g., C_(U2)) of a top memory cell (e.g., MC_(U2)) ofthe upper memory cell array MCA_(U). The length (dimension in the thirddirection D3) of the plate line PL₁ may be such that the plate line maybe coextensive in the third direction with the word lines.

According to the above description, the upper word line G1 and the lowerword line G2 may be formed to be laterally spaced apart from the bitline BL₁ and the plate line PL₁. Accordingly, the parasitic capacitancebetween the word line WL_(L1) and the capacitor C_(L1) may be decreased,and the parasitic capacitance between the word line WL_(L1) and the bitline BL₁ may be reduced.

The method of forming the memory cell MC_(L1) of FIGS. 7 to 10 mayinclude a process of forming the transistor T_(L1), a process of formingthe bit line BL₁, a process of forming the capacitor C_(L1), and aprocess of forming the plate line PL₁.

A process of forming the transistor T_(L1) will now be described. Anactive layer ACT may be formed to be vertically (i.e., in the firstdirection D1) spaced apart from the plane CP of a top surface of theperipheral structure 110, and gate dielectric layers GD1 and GD2 may beformed on the upper and lower surfaces of the active layer ACT.Subsequently, the upper word line G1 and the lower word line G2 may beformed over the gate dielectric layers GD1 and GD2, respectively.Subsequently, the first source/drain region T1 and the secondsource/drain region T2 may be formed through ion implantation of animpurity into the active layer ACT.

The bit line BL₁ may be formed to be vertically oriented from the planeCP of the peripheral structure 110. The bit line BL₁ may be formed to becoupled to the first source/drain region T1.

The process of forming the capacitor C_(L1) will now be described.First, a first node N1 may be formed to be coupled to the secondsource/drain region T2. Subsequently, a dielectric material N3 may beformed over the first node N1. Subsequently, a second node N2 may beformed over the dielectric material N3. A plate line PL₁ may be formedwhile the second node N2 is formed. The plate line PL₁ may be verticallyoriented from the plane CP of the peripheral structure 110.

FIGS. 11A to 11C are views illustrating a first node of a capacitorhaving a three-dimensional structure in accordance with anotherembodiment of the present invention. FIG. 11A shows a pillar-shapedfirst node LP, and FIGS. 11B and 11C show a first node N1 having a formof a pylinder, i.e., a combination of a pillar and a cylinder structure.

Referring to FIG. 11A, the first node N1 may be a lateral pillar LP. Alateral pillar LP may include a metal-based material, a silicon-basedmaterial, or a combination thereof. For example, the lateral pillar LPmay be formed of titanium nitride alone or may be formed of a stack oftitanium nitride and polysilicon.

Referring to FIGS. 11B and 11C, the first node N1 having the form of apylinder may include a lateral cylinder LC and a lateral pillar LP thatare parallel to the plane CP. Referring to FIG. 11B, the lateral pillarLP may be positioned in the inside of the lateral cylinder LC. Thelateral length of the lateral cylinder LC may be longer than the laterallength of the lateral pillar LP. For example, the inlet of the lateralcylinder LC may not be filled with the lateral pillar LP. Referring toFIG. 11C, the lateral cylinder LC may be formed in a lateral arrangementover the lateral pillar LP.

Referring to FIG. 11B, the lateral cylinder LC and the lateral pillar LPmay be of the same material or different materials. The lateral cylinderLC and the lateral pillar LP may include a metal-based material, asilicon-based material, or a combination thereof. For example, thelateral cylinders LC may be titanium nitride, and the lateral pillar LPmay be polysilicon.

Referring to FIG. 11C, the lateral cylinder LC and the lateral pillar LPmay be of the same material or different materials. The lateral cylinderLC and the lateral pillar LP may include a metal-based material, asilicon-based material, or a combination thereof. For example, thelateral cylinder LC and the lateral pillar LP may be of titaniumnitride. In addition, the lateral cylinder LC may be of titanium nitrideand the lateral pillar LP may be of polysilicon.

FIGS. 12A and 12B are views illustrating a memory device 200 and 200′ inaccordance with another embodiment of the present invention.

Referring to FIGS. 12A and 12B, the memory device 200 and 200′ mayinclude a peripheral circuit portion 210 and a memory cell array stackMCA. The memory cell array stack MCA may be the same as the memory cellarray stack MCA of FIG. 1 . The memory cell array stack MCA may includeDRAM memory cell array.

Referring to FIG. 12A, the memory cell array stack MCA may be positionedover the peripheral circuit portion 210. The peripheral circuit portion210 may correspond to the peripheral structure 110 of FIG. 1 .Accordingly, the memory device 200 may have a PUC (Peripheral UnderCell) structure. The memory cell array stack MCA may be positioned overthe semiconductor substrate 211 of the peripheral circuit portion 210.

Referring to FIG. 12B, the memory cell array stack MCA may be positionedunder the peripheral circuit portion 210. The peripheral circuit portion210 may correspond to the peripheral structure 110 of FIG. 1 . Forexample, in FIG. 1 , the peripheral structure 110 may be stacked abovethe memory cell array stack MCA. Thus, the memory device 200′ may have aCUP (Cell under Peripheral) structure. The memory cell array stack MCAmay be positioned under the semiconductor substrate 211 of theperipheral circuit portion 210.

The peripheral circuit portion 210 may refer to a circuit for drivingand controlling the memory cell array stack MCA during a drivingoperation (including a read or write operation) to a memory.

The peripheral circuit portion 210 may include an N-channel transistor,a P-channel transistor, a CMOS circuit, or a combination thereof. Theperipheral circuit portion 210 may include an address decoder circuit, aread circuit, and a write circuit. The peripheral circuit portion 210may include at least one circuit selected from sense amplifiers andsub-word line drivers. In an embodiment, the peripheral circuit portion210 may have a structure including a semiconductor substrate 211 and asense amplifier 212 arranged on the surfaces of the semiconductorsubstrate 211. The sense amplifier 212 may include a transistor SA_Tusing the semiconductor substrate 211 as a channel. The transistor SA_Tmay include a planar channel transistor whose channel is parallel to thesurface of the semiconductor substrate 211. The transistor structure inthe sense amplifier 211 may include a recess channel transistor, aburied gate transistor, and a fin channel transistor (FinFET) inaddition to the planar channel transistor.

The bit lines BL of the memory cell array stack MCA may be electricallyconnected to the transistor SA_T of the sense amplifier 211.

The bit lines BL and the transistor SA_T may be coupled to each otherthrough a multi-level metal line MLM 213. The multi-level metal line MLM213 may be formed by a Damascene process. It is understood thattransistor SA_T is described as an example of a plurality of transistorswhich may be included in the peripheral circuit portion 210.

Although not illustrated, according to another embodiment of the presentinvention, the memory device 200 and 200′ may include a firstsemiconductor substrate and a second semiconductor substrate bonded tothe first semiconductor substrate. The memory cell array stack MCA maybe formed over the first semiconductor substrate, and the peripheralcircuit portion 210 may be formed over the second semiconductorsubstrate. Each of the first semiconductor substrate and the secondsemiconductor substrate may include conductive bonding pads, and thefirst semiconductor substrate and the second semiconductor substrate maybe bonded to each other through the conductive bonding pads. Thus, thememory cell array stack MCA and the peripheral circuit portion 210 maybe electrically connected to each other.

According to embodiments of the present invention, it is possible toincrease cell density and to reduce parasitic capacitance by verticallystacking memory cells from a plane of a peripheral structure so as toform a three-dimensional structure.

According to embodiments of the present invention, interference betweenthe vertically stacked memory cells may be prevented because atransistor of a memory cell includes double word lines stacked with anactive layer therebetween.

According to embodiments of the present invention, since bit lines areformed as vertically oriented from a plane of a peripheral structure,bit line resistance may be reduced.

According to embodiments of the present invention, a memory device thatis highly integrated within a limited area may be realized by verticallystacking memory cells in the upper or lower portion of a peripheralcircuit portion.

While the present invention has been described with respect to specificembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit and scope of the invention as defined in the following claims.

What is claimed is:
 1. A memory device, comprising: a substrate; avertical conductive line oriented vertically over the substrate; anactive layer oriented laterally from the vertical conductive line; apair of line-shaped conductive lines disposed over the active layer; afirst node electrically connected to the active layer; a second nodeover the first node; and a dielectric material disposed between thefirst node and the second node, wherein the pair of line-shapedconductive lines comprises: a line-shaped lower conductive line disposedover a lower surface of the active layer; and a line-shaped upperconductive line disposed over an upper surface of the active layer. 2.The memory device of claim 1, wherein the active layer includes: a firstsource/drain region coupled to the vertical conductive line; a secondsource/drain region coupled to the first node; and a channel between thefirst source/drain region and a second source/drain region, and thefirst source/drain region, the channel, and the second source/drainregion are positioned in a lateral arrangement parallel to thesubstrate.
 3. The memory device of claim 2, wherein the pair ofline-shaped conductive lines are vertically stacked with the channeltherebetween.
 4. The memory device of claim 2, further comprising: agate dielectric layer which is formed between the pair of line-shapedconductive lines and the channel.
 5. The memory device of claim 1,wherein the lower and upper line-shaped conductive lines are set to thesame potential and are electrically connected to each other.
 6. Thememory device of claim 1, wherein the first node has a lateralcylindrical shape, and the second node includes: an inner second nodeextending into a cylindrical shape of the first node; and a plurality ofouter second nodes surrounding an outside of the cylindrical shape ofthe first node.
 7. A memory device, comprising: a memory cell arrayincluding a plurality of memory cells, wherein each of the memory cellcomprising: an active layer; and a pair of word lines disposed over theactive layer, wherein the pair of word lines comprises: a line-shapedlower word line disposed over a lower surface of the active layer; and aline-shaped upper word line disposed over an upper surface of the activelayer.
 8. The memory device of claim 7, wherein the line-shaped upperword line and the line-shaped lower word line are electrically connectedto each other
 9. The memory device of claim 7, further comprising: aperipheral circuit portion for controlling the memory cell array. 10.The memory device of claim 9, further comprising: a plurality of bondingpads, wherein the memory cell array and the peripheral circuit portionare electrically connected to each other through the bonding pads. 11.The memory device of claim 7, further comprising: a capacitorelectrically connected to the active layer.
 12. The memory device ofclaim 11, wherein the capacitor includes: a first node coupled to theactive layer; a second node on the first node; and a dielectric materialbetween the first node and the second node.
 13. The memory device ofclaim 12, wherein the first node of the capacitor has a lateralcylindrical shape, and the second node of the capacitor includes: aninner second node extending into the cylindrical shape of the firstnode; and a plurality of outer second nodes surrounding an outside ofthe cylindrical shape of the first node.